Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

A white LED lighting device driven by a pulse current is provided, which
consists of blue, violet or ultraviolet LED chips, blue afterglow
luminescence materials A and yellow luminescence materials B. Wherein the
weight ratio of the blue afterglow luminescence materials A to the yellow
luminescence materials B is 10-70 wt %:30-90 wt %. The white LED lighting
device drives the LED chips with a pulse current having a frequency of
not less than 50 Hz. Because of using the afterglow luminescence
materials, the light can be sustained when an excitation light source
disappears, thereby eliminating the influence of LED light output
fluctuation caused by current variation on the illumination. At the same
time, the pulse current can keep the LED chips being at an intermittent
work state, so as to overcome the problem of chip heating.

Claims:

1. A white LED lighting device driven by a pulse current, characterized
in that the white LED lighting device comprises blue, violet or
ultraviolet LED chips and luminescence material, the luminescence
material being a combination of blue afterglow luminescence material A
and yellow luminescence material B, a the yellow luminescence material B
being able to emit light under excitation of the blue, violet or
ultraviolet LED chips and/or excitation of the blue afterglow material B,
a weight ratio (A:B) between the blue afterglow luminescence material A
and the yellow luminescence material B being 10.about.70 wt %:30.about.90
wt %, the white LED lighting device driving the LED chips with a pulse
current having frequency of not less than 50 Hz.

2. The white LED lighting device driven by a pulse current according to
claim 1, wherein a weight ratio (A:B) between the blue afterglow
luminescence material A and the yellow luminescence material B is
20.about.50 wt %:50.about.80 wt %.

3. The white LED lighting device driven by a pulse current according to
claim 1, wherein the blue, violet or ultraviolet LED chips are internally
packed chips in the white LED lighting device.

4. The white LED lighting device driven by a pulse current according to
claim 1, wherein the device has a luminescence coating employing the
luminescence material.

5. The white LED lighting device driven by a pulse current according to
claim 1, wherein the blue afterglow luminescence material A has a peak
light-emitting wavelength of 440.about.490 nm.

6. The white LED lighting device driven by a pulse current according to
claim 1, wherein the blue afterglow luminescence material A is at least
one of Sr4Al14O25:Eu2+,Dy3+,
Sr2MgSi2O7:Eu2+,Dy3+, CaS:Bi3+,Na+,
CaS:Cu+,Na+ and CaSrS:Bi3+.

7. The white LED lighting device driven by a pulse current according to
claim 1, wherein the yellow luminescence material B has a peak
light-emitting wavelength of 520.about.580 nm.

8. The white LED lighting device driven by a pulse current according to
claim 1, wherein the yellow luminescence material B is a yellow
luminescence material with or without an afterglow phenomenon, or a
combination thereof.

9. The white LED lighting device driven by a pulse current according to
claim 1, wherein the yellow luminescence material B is at least one of
Y2O.sub.3.Al7O.sub.3.SiO7:Ce.B.Na.P,
Y7O2S:Mg,Ti, Sr3SiO5:Eu2+,Dy3+,
Ca2MgSi2O7:Eu2+,Dy3+, CaS:Sm3+, YAG:Ce and
TAG:Ce.

10. The white LED lighting device driven by a pulse current according to
claim 1, wherein the luminescence coating is formed by mixing the blue
afterglow luminescence material A and the yellow luminescence material B.

11. The white LED lighting device driven by a pulse current according to
claim 1, wherein the luminescence coating consists of a coating of the
blue afterglow luminescence materials A and a coating of the yellow
luminescence material B.

12. The white LED lighting device driven by a pulse current according to
claim 2, wherein a weight ratio (A:B) between the blue afterglow
luminescence material A and the yellow luminescence material B is
35.about.50 wt %:50.about.65 wt %.

13. The white LED lighting device driven by a pulse current according to
claim 12, wherein a weight ratio (A:B) between the blue afterglow
luminescence material A and the yellow luminescence material B is
40.about.50 wt %:50.about.60 wt %.

14. The white LED lighting device driven by a pulse current according to
claim 13, wherein a weight ratio (A:B) between the blue afterglow
luminescence material A and the yellow luminescence material B is 40 wt
%:60 wt %.

15. The white LED lighting device driven by a pulse current according to
claim 5, wherein the yellow luminescence material B has a peak
light-emitting wavelength of 520.about.580 nm.

16. The white LED lighting device driven by a pulse current according to
claim 6 wherein the yellow luminescence material B is at least one of
Y2O.sub.3.Al2O.sub.3.SiO2:Ce.B.Na.P,
Y2O2S:Mg,Ti, Sr3SiO5:Eu2+,Dy3+,
Ca2MgSi2O7:Eu2+,Dy3+, CaS:Sm3+, YAG:Ce and
TAG:Ce.

17. The white LED lighting device driven by a pulse current according to
claim 10, wherein the blue afterglow luminescence material A has a peak
light-emitting wavelength of 440.about.490 nm, and wherein the yellow
luminescence material B has a peak light-emitting wavelength of
520.about.580 nm.

18. The white LED lighting device driven by a pulse current according to
claim 10, wherein the blue afterglow luminescence material A is at least
one of Sr4Al14O25:Eu2+,Dy3+,
Sr2MgSi2O7:Eu2+,Dy3+, CaS:Bi3+,Na+,
CaS:Cu+,Na+ and CaSrS:Bi3+, and wherein the yellow
luminescence material B is at least one of
Y2O.sub.3.Al2O.sub.3.Si0.sub.2:Ce.B.Na.P,
Y2O2S:Mg,Ti, Sr3SiO5:Eu.sup.2.+-.,Dy3+,
Ca2MgSi2O7:Eu2+,Dy3+, CaS:Sm3+, YAG:Ce and
TAG:Ce.

19. The white LED lighting device driven by a pulse current according to
claim 11, wherein the blue afterglow luminescence material A has a peak
light-emitting wavelength of 440.about.490 nm, and wherein the yellow
luminescence material B has a peak light-emitting wavelength of
520.about.580 nm.

20. The white LED lighting device driven by a pulse current according to
claim 11, wherein the blue afterglow luminescence material A is at least
one of Sr4Al14O25:Eu2+,Dy3+,
Sr2MgSi2O7:Eu2+,Dy3+, CaS:Bi3+,Na+,
CaS:Cu+,Na+ and CaSrS:Bi3+, and wherein the yellow
luminescence material B is at least one of
Y2O.sub.3.Al2O.sub.3.SiO2:Ce.B.Na.P,
Y2O2S:Mg,Ti, Sr3SiO5:Eu.sup.2.+-.,Dy3+,
Ca2MgSi2O7:Eu2+,Dy3+, CaS:Sm3+, YAG:Ce and
TAG:Ce.

Description:

FIELD

[0001] The present invention relates to a white LED lighting device using
afterglow characteristic of the luminescence powder and driven by a pulse
current, which belongs to the field of LED manufacturing. The present
invention more particularly relates to a white LED lighting device
prepared using blue afterglow luminescence materials and yellow
luminescence materials.

BACKGROUND

[0002] Currently, the LED is used in the fields such as lighting, display,
backlight, etc., and as the most promising lighting means of the next
generation, the LED gains extensive attention with the advantages of
being energy saving, durable, pollution free, etc. There are many
solutions for implementing the white LED, wherein the most mature
technical solution for preparing the white LED at present is to realize
the white light emission using a combination of the blue LED chip and the
yellow phosphor. Volume 11 page 53 of AppLPhys.Lett. published in 1967
reports a luminescence material Y3Al5O.sub.12:Ce3+, which
has a yellow luminescence with a maximum light-emitting wavelength of 550
nm and a life of less than 100 ns. Volume 64 page 417 of AppLPhys.A
published in 1997 reports that the white LED light emission is realized
using the yellow luminescence of Y3Al5O.sub.12:Ce3+ and
the blue gallium nitride, and such technology is the most mature
technical solution for preparing the white LED at present. The existing
LED chips are mainly driven by the direct current having constant
magnitude and direction. But in such a mode, the LED thermal design
requirement is very high, and the LED chips will be burnt out if the
extra heat cannot be dissipated in time.

[0003] The Chinese patent No. CN100464111C discloses an alternating
current (AC) LED lamp using LED chips of different colors connected in
parallel in an AC power source. The patent mainly describes that the LED
chips of different colors together form white light, and recites the
specific circuit such as red, green and blue light emitting chips,
without mentioning the luminescence powder. The American U.S. Pat. No.
7,489,086,B2 discloses an AC LED driving apparatus and a lighting device
using the same. The patent also emphasizes on the circuit structure
without making an innovation report about the luminescence powder, and
the conventional luminescence powder Y3Al5O.sub.12:Ce3+ is
still employed. The inventor of the present invention researches a
luminescence material Y2O3.Al2O3.SiO2:Ce.B.Na.P
having the yellow long afterglow phenomenon and a white LED lighting
device driven by a pulse current (the Chinese patent application No.
200910307357.3). However, the white LED lighting device using the pulse
current driving mode and the afterglow characteristic of the luminescence
powder to compensate the light output fluctuation in the present
invention is still not reported.

SUMMARY

[0004] The objective of the present invention is to provide a white LED
lighting device driven by a pulse current.

[0005] The technical solution of the present invention: blue LED chips or
ultraviolet chips driven by a pulse current+blue afterglow luminescence
materials A+yellow luminescence materials B. Wherein the weight ratio of
the blue afterglow luminescence materials A to the yellow luminescence
materials B is 10-70 wt %: 30-90 wt %, and preferably 20-50 wt %:50-80 wt
%. The white LED lighting device drives the LED chips with a pulse
current having a frequency of not less than 50 Hz.

[0006] The present invention implements a white LED lighting device driven
by a pulse current, thereby enabling the LED chips to work periodically
and intermittently. Meanwhile, the luminescence powder used by the
present invention has the afterglow effect, which can compensate the
light output fluctuation of the lighting device caused by the periodic
variation of the pulse current.

[0007] Further, the blue afterglow luminescence material A has a peak
light-emitting wavelength of 440˜490 nm.

[0008] Further, the blue afterglow luminescence material A is at least one
of Sr4Al14O25:Eu2+,Dy3+,
Sr2MgSi2O7:Eu2+,Dy3+, CaS:Bi3+,Na+,
CaS:Cu+,Na+ and CaSrS:Bi3+.

[0012] The white light emitted by the white LED lighting device of the
present invention is formed of the blue light emitted by the blue
afterglow luminescence powder, the yellow light emitted by the yellow
luminescence powder and the light from the blue or ultraviolet LED chip
under the excitation of the chip.

[0013] The above luminescence powder may also be excited by the violet and
ultraviolet LED chips, thereby achieving the same effect.

[0014] The luminescence coating of the present invention may be formed by
mixing the blue afterglow luminescence materials A and the yellow
luminescence materials B, or coating the blue afterglow luminescence
materials A on the chips and then coating the yellow luminescence
materials B on the blue afterglow luminescence materials A.

[0015] The principle of the white LED lighting device driven by the pulse
current in the present invention is as follows:

[0016] From the schematic diagram of the basic module of the LED lighting
device as shown in FIG. 1, it can be seen that due to the pulse periodic
characteristic of the pulse current, the luminescence of the device also
has a periodic bright-dark change, i.e., luminescence strobing, thereby
influencing the usage of the device.

[0017] The present invention employs the luminescence materials having the
afterglow characteristics so that the light will be sustained when the
excitation light source disappears, thus in the white LED lighting device
driven by the pulse current based on the solution of the present
invention, when the current cycle is changed to the small current stage,
the blue afterglow material will emit the blue afterglow to compensate
the blue light and excite the yellow luminescence powder, thereby
eliminating the influence of the luminescence strobing of the LED chip
caused by the pulse current fluctuation, so that the light output of the
device during the pulse cycle is kept stable. In addition, since the LED
chip does not work in a half of each pulse cycle, the thermal effect
decreases, which is beneficial to overcome the series of difficulties
caused by chip heating in the usage of the existing white LED lighting
device. Moreover, the white LED lighting device driven by the pulse
current in the present invention achieves a good heat dispersion and a
long service life without using any complex circuit switching device,
which obviously reduces the cost.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 is a schematic diagram of a basic LED lighting device driven
by a pulse current;

[0021]FIG. 4 is a photoluminescence spectrum of
Y2O3.Al2O3.SiO2:Ce.B.Na.P; and FIG. 5 is a
schematic diagram of the structure of an LED luminescence unit, in FIG.
5-1, 1 denotes a mixed luminescence coating made of blue afterglow
luminescence materials A and yellow luminescence materials B; 2 denotes a
blue, violet or ultraviolet LED chip; and 3 denotes a lens; and in FIG.
5-2, 2 denotes a blue, violet or ultraviolet LED chip; 3 denotes a lens;
5 denotes a coating made of blue afterglow luminescence materials A; and
4 denotes a coating made of yellow luminescence materials B.

[0022] The above contents of the present invention are further described
in details through the following embodiments in the form of examples. But
it shall be appreciated that the subject scope of the present invention
is not limited to the following examples, and any technology implemented
by the above contents of the present invention shall fall within the
scope of the present invention. In the examples, the pulse current has a
frequency of 100 Hz, the blue LED chip has an emission wavelength of 460
nm, the violet LED chip has an emission wavelength of 400 nm, and the
ultraviolet LED chip has an emission wavelength of 365 nm.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] A new white LED lighting device consists of blue LED chips, blue
afterglow luminescence materials A and yellow luminescence materials B.
Wherein the weight ratio of the blue afterglow luminescence materials A
to the yellow luminescence materials B is 10-70 wt %:30-90 wt %, and
preferably 20-50 wt %:50-80 wt %. The white LED lighting device drives
the LED chips with the pulse current having a frequency not less than 50
Hz.

[0024] Wherein the blue afterglow luminescence material A has a peak
light-emitting wavelength of 440-490 nm, e.g., it may be one or
combinations of Sr4Al14O25:Eu2+,Dy3+,
Sr2MgSi2O7:Eu2+,Dy3+, CaS:Bi3+,Na+,
CaS:Cu+,Na+ and CaSrS:Bi3+.

[0025] The yellow luminescence material B may be a luminescence material
having or not having the afterglow phenomenon, or a combination thereof,
with a peak light-emitting wavelength of 520-580 nm. The luminescence
material having the afterglow phenomenon includes Ce-activated
Y2O3.Al2O3.SiO2:Ce.B.Na.P,
Y2O2S:Mg,Ti, Sr3SiO5:Eu2+, Dy3+,
Ca2MgSi2O7:Eu2+,Dy3+ and CaS:Sm3+. The
luminescence material not having the afterglow phenomenon includes YAG:Ce
and TAG:Ce.

[0026] The white light emitted by the white LED lighting device of the
present invention is formed of the blue light emitted by the blue
afterglow luminescence powder, the yellow light emitted by the yellow
luminescence powder and the light from the blue LED chip under the
excitation of the blue LED chip.

[0027] The present invention employs the luminescence materials having the
afterglow characteristics so that the light will be sustained when the
excitation light source disappears, thus in the white LED lighting device
driven by the pulse current based on the solution of the present
invention, when the current cycle is changed, the blue afterglow material
will emit the blue afterglow to compensate the blue light and excite the
yellow luminescence powder, thereby eliminating the influence of the
luminescence strobing of the LED chip caused by the pulse current
fluctuation on the illumination, so that the light output of the device
during the pulse cycle is kept stable. In addition, since the LED chip
does not work in a half of each pulse current cycle, the thermal effect
decreases, which is beneficial to overcome the series of difficulties
caused by chip heating in the usage of the existing white LED lighting
device.

[0030] The preparation method is as follows: 500-mesh-screening
luminescence materials A and B, uniformity mixing the luminescence
materials A and B in the ratios described in Examples 1-18, and packing
them with an LED chip having the power of 0.1 W, so as to form a white
LED lighting device with its basic unit as shown in FIG. 1, and the pulse
current has a frequency of 100 Hz.

Test Example 1 Luminescence Characteristics of the LED Lighting Device of
the Present Invention

[0031] The pulse current used in the present invention has a frequency of
100 Hz, i.e., the cycle is 10 ms. Table 2 gives the brightness within 20
ms tested by the lighting device shown as the module in FIG. 1 with a
high-speed camera shooting 300 photos per second, when the LED chips
given in Examples 1-18 are directly powered by the AC mains supply. The
reference sample is an LED lighting device driven by a pulse current
formed in the same manner with a white LED chip having the commercially
available blue chip packed with the yellow luminescence material. The
brightness data in Table 2 is the relative test brightness of the
instrument and has no dimension.

[0032] As can be seen from the data in Table 2, the luminescence of the
present invention is stable during the pulse current cycle, while the
luminescence of the white LED lighting device using the commercially
available blue chip packed with the conventional yellow YAG luminescence
material having no afterglow is unstable, and fluctuates very obviously
during the pulse current cycle.

Test Example 2 Light Attenuation of the LED Lighting Device of the Present
Invention

[0033] Table 3 shows the light attenuation data of Examples 1-18 and the
reference sample. The reference sample is a lighting device formed by
installing the white LED chip having the commercially available blue chip
packed with the yellow luminescence material in the general direct
current (DC) power supply mode at present. The test method is as follows:
powering on the LED lighting devices driven by the pulse current of
Examples 1-18 and the reference sample, and testing their brightness at a
certain interval. The results are shown in Table 3, wherein the data is
relative brightness and normalized with the initial data.

[0034] As can be seen from the data in Table 3, the brightness attenuation
of the white LED lighting device driven by the pulse current of the
present invention is less than that of the LED lighting device using the
existing mode.

[0035] The data of Tables 2-3 indicates that the white LED lighting device
driven by the pulse current prepared with the afterglow luminescence
materials in the present invention is advantageous in stable luminescence
and small light attenuation, thereby having obvious novelty and
inventiveness over the existing LED lighting device.